GU tacho

Hi I’ve got my conversion up and running (TD42T into ZD) and just wondering what everyone’s thoughts are on the Dakota digital tacho correction units. I got Killa Kustom Kables to make the loom for me and they did a great job, plugged it in and turned the key and it ran. The thing is that with the converter set to 6 cylinders in and 4 out like it was set and the instructions say it didn’t even register at idle and out on the road I could only get it to about 1500 rpm on the gauge. I have played around with it and the closest I can manage to get it to reading true is set at 5 in and 6 out but it’s still not quite right according to what rpm I used to have at 100 kph. It also seems to be slow to respond and the needle is a bit jumpy. I tried to call Killa kustoms but haven’t been able to get through to quiz them just thought I’d ask if anyone else has had similar issues? Cheers.